As an example of the background technique related to the present invention, reference will be made below to a shift range switching system wherein a shift range switching mechanism in a vehicular automatic transmission is operated by a rotary actuator using an electric motor.
In this type of a shift range switching system, in accordance with a shift range switching command (set by an occupant) issued by shift range setting means (e.g., a shift lever, a shift range setting button, or a joy stick), the rotational direction, speed, quantity and angle of an electric motor are controlled to switch an actual shift range (an actual shift range in an automatic transmission) in a shift range switching mechanism.
According to this construction, since there is no mechanical connection between the shift range setting means and the shift range switching mechanism, the freedom of on-board installation of the shift range setting means and the shift range switching mechanism is increased.
When there is a mechanical connection between the shift range setting means and the shift range switching mechanism, the shift range switching command set by the shift range switching means and the actual shift range in the shift range switching mechanism coincide with each other positively unless the mechanical connection is damaged.
However, when there is no mechanical connection between the shift range setting means and the shift range switching mechanism, it is likely that the shift range switching command set by the shift range setting means and the actual shift range in the shift range switching mechanism may not be coincident with each other by some unexpected cause.
When the shift range switching command and the actual shift range do not coincide with each other, it is likely that the vehicle may start at the time of start-up of the engine despite the driver having an understanding that the vehicle will not start. In this case, driver has a sense of incongruity. Therefore, in a shift range switching system wherein there is no mechanical connection between shift range setting means and a shift range switching mechanism, it is necessary to prevent an unintended starting of the vehicle at the time of start-up of the engine even when there occurs any unexpected factor.
JP 2002-323127A shows a shift range switching system in which an actual shift range (the last-time shift range) at the time of stopping an engine is stored in a non-volatile memory or the like and, when starting the operation of the engine, “the last-time shift range” which has been stored at the time of engine stop is made the present “actual shift range.”
In this shift range switching system, when an output shaft rotates while a rotary actuator is once dismounted for maintenance or the like, it is likely that “the last-time shift range” stored in memory and “actual shift range” after maintenance and mounting may be different from each other. Thus, even when “the last-time shift range” stored in memory is “N” or “P” range, the present “actual shift range” may be another shift range (e.g., such a vehicular travel range as R, “D”, 2, or L). Therefore, when there is made control for replacing “the last-time shift range” with “actual shift range” at the time of start-up of the engine, it is necessary to take a measure for preventing an unintended starting of the vehicle.